Abstract 1364: Spatially-resolved in situ expression profiling using the GeoMx™ Cancer Transcriptome Atlas panel in FFPE tissue

The emerging field of spatial genomics represents a significant advance for biology. To drive new discoveries in spatial genomics and immuno-oncology, we introduce the GeoMx Cancer Transcriptome Atlas (CTA) Panel for comprehensive spatial analysis of cancer pathways using the Nanostring GeoMx Digital Spatial Profiler (DSP). We demonstrate profiling of 1600+ immuno-oncology targets in the tumor, microenvironment, and immune compartments of archival FFPE tissue sections, coupled to downstream Next Generation Sequencing (NGS) readout to enable high-throughput workflows. High-plex spatial RNA molecular profiling with GeoMx CTA was performed as follows: 1. Photocleavable DNA oligonucleotides tags were coupled to 8000+ in situ hybridization probes targeting 1600+ genes. These reagents were allowed to bind targets directly on slide-mounted FFPE tissue sections. 2. ROIs were identified and selected using GeoMx DSP, and ROI-specific oligonucleotide tags were released using ultraviolet exposure. 3. Released oligonucleotide tags from each ROI were collected and deposited into designated wells on a microtiter plate, allowing well indexing of each ROI during NGS library preparation. 4. After indexing, the entire plate was pooled into a single tube for purification and then sequenced on an Illumina instrument. 5. NGS reads were processed into digital counts and mapped back to each ROI, generating a map of transcript activity within the tissue architecture. We compared data from experiments in which bulk RNA-seq and GeoMx DSP using the CTA Panel were performed on the same samples. Overall, we found good correlation between pseudo-bulk GeoMx CTA (sum of ROIs) and RNA-seq from the same tissue specimen. Individually, however, each ROI showed a distinct expression pattern from bulk, and ROI expression patterns clustered based on similar tissue morphology. Importantly, GeoMx CTA was able to detect a higher number of genes with low expression within the microenvironment and immune spatial compartment compared to bulk RNA-seq, providing a detailed look at the anti-tumor immune response. Lastly, we profiled similar tissues using a novel 18000+ gene whole transcriptome panel and found further enrichment of low-expressers relative to RNA-seq, revealing novel spatial biology previously masked by bulk assays. Together, these data demonstrate that GeoMx offers high sensitivity for genome-scale expression profiling while preserving critical information about tissue architecture. GeoMx